The process of microbial remediation is a complex one. Firstly, an environment is identified as toxic. For example, this may be an oil spill of creosote containing large amounts of polycyclic aromatic hydrocarbons (PAHs), which are extremely toxic to the environment. A microbial community is then placed in contact with the contaminated site and depending on the microbe, either immobilisation or mobilisation of the contaminant may occur. With the occurrence of mobilisation, heterotrophic or autotrophic leaching is performed by the microbial community. This ‘leaching’ solubilises heavy metals through a range of chemical reactions. For example, the production of sulfuric acid via autotrophic leaching has led to the solubilisation of metals within sewage contaminated areas. It has also been found that autotrophic leaching is a more effective way of controlling contamination than heterotrophic leaching (Gadd, 2004).
However, if immobilisation occurs, the potential of solubilisation through a series of equilibrium shifts within the contaminant increases. Both methods have proved to be a success (Gadd, 2004). The microbial community then absorbs the contaminant when it is in a soluble state.
Table 1. Demonstrates the desired conditions for aerobic microbial remediation.
Desired conditions
Microbial population
Suitable kinds of organisms that can biodegrade all the contaminants.
Oxygen
Enough to support aerobic biodegradation (about 0.4 mg/L in the soil water).
Water
Soil moisture should be from 50-70% of water holding capacity of the soil.
Nutrients
Nitrogen, phosphorus, sulfur.
Temperature
Appropriate temperatures for microbial growth (0-40˚C).
However, if immobilisation occurs, the potential of solubilisation through a series of equilibrium shifts within the contaminant increases. Both methods have proved to be a success (Gadd, 2004). The microbial community then absorbs the contaminant when it is in a soluble state.
Table 1. Demonstrates the desired conditions for aerobic microbial remediation.